The present invention has utility in the field of data recording and playback. It is useful, for example, in controlling the radial position of a write/read head relative to the recording surface(s) of a data storage disk (e.g. magnetic, magneto-optic, and optical disks) so that information can be written on (or read from) a desired data track.
Heretofore, a variety of radial access mechanisms have been proposed and utilized to control the radial position of a write/read head relative to a data storage disk. Typically, such mechanisms function to advance the write/read head along straight or circular trajectories in a plane parallel to the plane of disk rotation. For straight head motion, both stepping and linear motors of various designs have been used. With a stepping device, the rotary motion of the motor shaft is commonly converted to linear motion by a lead screw, rack and pinion combination, or quite often by a split band wrapped around the motor shaft. For a linear motor, such as a voice-coil motor, its motion is directly coupled to a movably-mounted carriage which supports the head. Voice-coil motors are also used in circular trajectory schemes where a rotary arm carrying the head turns about a pivot. Regardless of the driving scheme, however, the head carriage is suspended in most cases by a number of bearings or bushings that require precise alignment and high precision in parts manufacture to avoid the problems associated with backlash and friction. Even with those requirements fulfilled, execution of a discrete submicron translation (typical for recording and reading data when the track density is extremely high) cannot be easily achieved. This may be attributed, in part, to the relatively high start-up torque required to overcome the stick-slip friction which is characteristic of any bearing operation. Also, it is complicated by the fact that the so-called Brinelling effect shortens the bearing's life when the bearing balls or rollers are subjected to small oscillations about the same point. Furthermore, internal clearances present in any bearing assembly may cause dynamic problems.
One attempt to resolve the above problems was made by developing the so-called "gyro gimbal" bearings, now offered by several different manufacturers. Their design consists of a three-ring assembly comprising a single row bearing positioned within a rigid double row bearing with closely controlled radial and axial play. While the outer ring with an enlarged flange provides accurate mounting to the stationary structure, the inner ring supports the gimbal. These specially designed gimbal bearings, however, are quite small and cannot be easily utilized in disk drive mechanisms.